Brown's novels are treasure hunts set in a 24-hour period, and feature the recurring themes of cryptography, keys, symbols, codes, and conspiracy theories. His books have been translated into 52 languages, and as of 2012, sold over 200 million copies. Two of them, The Da Vinci Code and Angels & Demons have been adapted into films.

Brown's interest in secrets and puzzles stems from their presence in his household as a child, where codes and ciphers were the linchpin tying together the mathematics, music and languages in which his parents worked. The young Brown spent hours working out anagrams and crossword puzzles, and he and his siblings participated in elaborate treasure hunts devised by their father on birthdays and holidays. At Christmas, for example, Brown and his siblings did not find gifts under the tree, but followed a treasure map with codes and clues throughout their house and even around town to find the gifts.

Dan's third novel

Dan's first novel

While on holiday in Tahiti in 1993, Brown read Sidney Sheldon's novel The Doomsday Conspiracy and was inspired to become a writer of thrillers. So, in 1996 Brown quit teaching to become a full-time writer. Digital Fortress was published in 1998. His wife, Blythe, did much of the book's
promotion, writing press releases, booking Brown on talk shows, and
setting up press interviews. Subsequently he wrote Angels & Demons(ebook) and Deception Point(ebook), released in 2000 and 2001 respectively, the former of which was the first to feature the lead character, Harvard symbology expert Robert Langdon. Brown's first three novels had little success, with fewer than 10,000 copies in each of their first printings. His fourth novel, The Da Vinci Code(ebook), became a bestseller, going to the top of the New York Times Best Seller list during its first week of release in 2003. It is now credited with being one of the most popular books of all time, with 81 million copies sold worldwide as of 2009.